Initial Experience with Exoscopic-Based Intraoperative Indocyanine Green Fluorescence Video Angiography in Cerebrovascular Surgery: Assessment of Feasibility, Safety, and Next Generation Form-Factor

Background: Technological evolutions in cerebrovascular surgery (CVS) have greatly reduced morbidity, especially with real-time visualization of two primary sources: (1) native vessel patency and (2) residual lesion. Microdoppler and indocyanine green fluorescence-microscopy (ICG-M) have emerged as potential replacements of intraoperative angiography (IA), while digital subtraction angiography (DSA) remains the gold standard. Recent studies have shown a potential benefit of exoscopic visualization in microsurgery, with more recent applications to CVS. The feasibility of ICG in conjunction with exoscopic visualization (ICG-E), to our knowledge, has not yet been reported for CVS.

Objective: This study aims to provide initial experience with an exoscopic-based ICG video angiography in CVS.

Methods: Retrospective cohort study with two inclusion criteria: (1) ICG-E was the primary method of determining patency and residual lesion; and (2) confirmatory postoperative DSA was performed. ICG-E consisted of two form factors: (1) exoscopic-coupled or (2) self-contained handheld imager. Chart review was undertaken to analyze ICG dosage, perioperative complications, work flow/setup time, and the concordance of ICG-E with IA and postoperative DSA. Stratification was based on form factor used, pathology, location, size, grade, and rupture status.

Results: Eleven patients met the inclusion criteria, eight aneurysms (two ruptured and six unruptured), and three arteriovenous malformations (AVMs; 1 previously ruptured). ICG-E was feasibile in all cases. There were two residual aneurysmal necks noted on the ICG-E (middle cerebral artery [MCA]) that were intentional to avoid flow-obstructive stenosis. There was an additional remnant posterior communicating artery (PCoA) infundibulum, which was not clipped to preserve the fetal posterior cerebral artery (PCA). No clinical sequalae were noted. IA was used if there was a question of stenosis, residual, or complex geometery, yielding seven aneurysm cases with a concordance of 88% with ICG-E and 88% with postoperative DSA . Case 4 (MCA) demonstrated discordance between ICG-E and DSA, with DSA revealing stenosis of the MCA superior division. All AVM cases were fully obliterated, with 100% concordance between ICG-E, IA, and DSA. ICG dosage “per run” averaged 4.2 mg per dose and ranged from 1 to 4 doses per case. Total ICG received per patient averaged 10.2 mg. There were no intra- or perioperative complications noted. The last four cases (two aneurysms and two AVMs) utilized the handheld system, whereas the previous cases utilized an exoscopically coupled ICG detection unit.

Conclusion: In this preliminary, hypothesis-generating study, ICG-E was a safe and feasible means of providing real-time cerebrovascular visualization. We noted a preferential transition into the more readily accessible handheld form factor, a more portable, less resource-dependent and readily accessible real-time imaging modality. Larger studies will be needed to assess broader safety, dose escalation, and efficacy data to validate the hypothesis.

No conflict of interest has been declared by the author(s).